The United States government has sponsored emergency alert systems to notify the public about severe weather and other public emergencies. The emergency alert systems use sirens and flashing lights for local emergency notifications. With the deployment of radio and television networks, radio and television signals have also been used to broadcast emergency alerts to user radios and televisions. In 2006, the federal government enacted a Commercial Mobile Alert System (CMAS) that broadcasts emergency notifications to wireless phones in dynamically-specified CMAS broadcast areas.
Long Term Evolution (LTE) networks are geographically sectioned into Tracking Areas (TAs) to locate wireless phones for paging and other wireless communication services. When the CMAS issues emergency CMAS information, the CMAS includes the Tracking Area Codes (TACs) for the TAs that overlay the specified CMAS broadcast area. In the LTE network, a Mobility Management Entity (MME) receives the CMAS information and the TACs from the CMAS.
The MME transfers the CMAS information and the TACs to evolved NodeBs (eNodeBs) in the LTE network. The eNodeBs in the TACs will detect their own TAC and responsively broadcast the CMAS information to LTE User Equipment (UEs). The CMAS information broadcast typically uses LTE System Information Blocks (SIBs) 1 and 12. The LTE UEs wirelessly receive the CMAS information and responsively alert their users and display the CMAS information. For example, the LTE UEs around the location of a child abduction would wirelessly receive CMAS Amber Alerts, and in response, the LTE UEs would alert their users and display information about the child abduction in hopes of saving the child with public support.
The LTE networks are deploying wireless relays to extend their wireless communication service footprint. The wireless relays have internal LTE eNodeBs to serve LTE UEs. The wireless relays also have internal relay-UEs that communicate with macro LTE eNodeBs. Thus, a wireless relay eNodeB communicates with its serving macro eNodeB over the relay-UE. Unfortunately, these wireless relays have not been optimized to broadcast CMAS information in an effective and efficient manner.